Hypoventilation and apnea are the most common causes of hypoxemia in perioperative patients. Supplementing oxygen and/or providing mechanical ventilation (non-invasive or invasive) is an essential approach to correcting hypoxemia and avoiding serious consequences associated with hypoxemia. Currently, oxygen supplementation is usually achieved through either a nasal cannula or a face mask (including simple face mask, partial rebreathing face mask, nonrebreathing face mask, Venturi mask, face oxygen tent). Nasal cannulas and face masks are very useful in patients who have mild respiratory depression or in patients who do not have respiratory depression but have other medical conditions that can cause hypoxemia. In patients with hypoventilation and apnea, mechanical ventilation (non-invasive or invasive) is the most effective approach to achieve adequate ventilation and to correct hypoxemia. Non-invasive ventilation (NIV) is usually used first to achieve adequate ventilation and oxygenation prior to endotracheal intubation (invasive ventilation). However, existing conventional nasal cannulas and face masks can only be used for delivering oxygen and cannot be used for NIV. To perform NIV, the nasal cannula or the face mask must be removed first and then a ventilation face mask or nasal mask will be placed on a patient's face or nose. Once the patient's condition improves and the patient regains the ability to maintain adequate spontaneous ventilation and oxygenation, the ventilation face mask or nasal mask will be replaced with a conventional nasal cannula or face mask in order to maintain adequate oxygenation. It is inconvenient to frequently switch back and forth between a conventional nasal cannula or face mask and a ventilation face or nasal mask, especially in patients with labile respiratory function.
Recently, high-flow nasal cannula (HFNC) oxygen delivery has been gaining attention for critically ill patients who are not candidates for NIV. HFNC has been shown to decrease the frequency and the work of breathing and reduce needs for escalation of respiratory support in patients with diverse underlying diseases such as hypoxemic respiratory failure, acute exacerbation of chronic obstructive pulmonary disease (COPD) and acute heart failure. There are several HFNCs available in the market. They include Optiflow (trademark) HFNC (manufactured by Fisher&Paykel Healthcare Inc), Vapotherm HI-VNI (trademark) (manufactured by Vapotherm Inc), AquaNASE (trademark) nasal cannula (manufactured by Armstrong Medical, Inc), and ACUCARE (trademark) (manufactured by ResMed, Inc). They can deliver a heated and humidified air/oxygen at a flow rate of up to 60 liters per minute (lpm). The patient interfaces have two enlarged nasal prongs that are placed in a patient's nostrils, but the nasal prongs do not create a seal between the nasal prongs and the nares. Thus, HFNC cannot actively enhance tidal volume. None of the existing HFNCs can be used for NIV because they neither push during inspiration nor pull during expiration. To perform NIV, HFNC must be removed and a ventilation face mask or nasal mask will be placed on a patient's face or nose. Since HFNC is usually used for critically ill patients who are otherwise the candidates for NIV or invasive ventilation, switching between high-flow oxygen therapy and NIV will become even more frequent. Thus, there is a need for a patient interface that can be used for both high-flow oxygen therapy and NIV so that high-flow oxygen therapy and NIV can be switched without changing the patient interface.
NIV means ventilatory support without an endotracheal or tracheotomy tube. It has been widely used to treat acute or chronic respiratory failure and has been considered the standard care for acute exacerbations of COPD and severe acute cardiogenic pulmonary edema. Clinical studies have demonstrated that NIV is equivalent in efficacy to conventional mechanical ventilation. NIV has been also applied to prevent or to treat perioperative respiratory failure. It is particularly useful in patients at high risk of postoperative respiratory failure such as morbid obese, preexisting lung diseases, thoracic and cardiac surgeries, and upper abdominal surgery. The use of NIV has been shown to effectively prevent or treat acute respiratory failure and to avoid endotracheal intubation in the post-operative period. The benefits of NIV include lower complication rates, shorter duration of hospital stay, lesser cost of treatment, and reduced morbidity and mortality rates.
However, NIV has a very high failure rate, ranging between 18% and 40% in the acute setting. Although the success of NIV depends on many factors, such as patient selection, underlying pathology, the severity of acute respiratory failure, and expertise with NIV, interface choice is one of the key factors determining the success of NIV. The commonly used interfaces for NIV include nasal masks, orofacial masks, full face masks, mouthpieces, nasal pillows, and helmets. Each of them has its own advantages and disadvantages and clinical trials have not demonstrated the superiority of any interface. The common problems associated with orofacial masks and nasal masks include air leaks, noise, discomfort, skin lesions, and conjunctivitis. These problems are the common reasons for poor patient compliance and high NIV failure rates. To overcome interface-related problems and increase patient compliance, several nasal interfaces have been manufactured to replace nasal or face masks for attaining CPAP and NIV. These nasal interfaces include Nasal Aire II (trademarked) (manufactured by InnoMed Technologies, Inc), Bravo (trademarked) nasal pillow CPAP mask (manufactured by InnoMed Technologies, Inc), Swift TM FX (trademarked) nasal pillow (manufactured by ResMed, Inc) and AirFit P10 (trademarked) nasal pillow (ResMed, Inc). They completely seal the nostrils and prevent air leakage during inhalation and exhalation. These nasal interfaces are more comfortable to wear and have increased patient comfort and compliance. However, there are still some drawbacks with the existing nasal interfaces. First, the existing nasal interfaces seal the nostrils by forming airtight barriers either inside the nostrils or outside the nostrils. None of them provide airtight seal in both inside and outside the nostrils. Thus, excessive pressure must be applied to the nose to prevent air leaking, which causes significant discomfort for patients. Secondly, the existing nasal interfaces use single limb patient circuits for delivering gases from the flow generator or ventilator to the nasal interfaces, and require exhaust or vent holes at, near or adjacent to the nasal interfaces for discharging the patient's expired breathing gases. Thus, gases are continuously leaking through the exhaust or vent holes during use. This continuous air leaking through the exhaust or vent holes has several disadvantages: 1) high flow rates are needed to compensate for air leaks; 2) larger patient circuits are needed to deliver high flow of gases from the ventilator to the patient interfaces; 3) the air exhaust through the exhaust or vent holes creates a loud noise which is disturbing and irritating the patients during use. Thirdly, the patients cannot breathe naturally and have difficulty breathing out during exhalation because a minimum-required pressure of 4 centimeters of water (cmH2O) is constantly provided during use in order to facilitate discharging the expired gases. Thus, there is a need for a patient interface that can be used for CPAP and NIV with less airflow and reduced noise level.
U.S. Pat. No. 6,679,265, issued Jan. 20, 2004 to Strickland and Lee discloses a patient interface which includes a pair of nasal inserts which are fed bilaterally by a pair of delivery tubes. The nasal inserts seal the nostrils by forming airtight barriers inside the nostrils and a simple head strap is used to support the interface. The device of Strickland and Lee is lightweight and more comfortable to wear. However, like all other existing nasal interfaces, the exhaust ports are positioned near the nose and the delivered gases will continuously leak through the exhaust ports during inhalation and exhalation. The patient cannot inspire air from the outside of the interface during inhalation and all airflow is supplied by a flow generator. Thus, high flow rates are required to obtain the desired therapeutic pressures. Furthermore, the air exhaust through the exhaust ports constantly makes a loud noise during use and the interface is not ideal for delivering gases and monitoring end tidal carbon dioxide (EtCO2) when NIV is not needed.
Thus, there is a need for an improvement which overcomes the aforementioned problems of the prior art devices and provides a nasal interface that can be used for both delivering high flow of gases and providing CPAP and NIV and that improves patient comfort and increases patient compliance.